1. Field of the Invention
The present invention relates to a cylindrical elongated vertical furnace for simultaneous treatment of material at high temperature, preferably above 1000.degree.C in a gaseous atmosphere under high pressure, preferably above 500 bar.
2. The Prior Art
Pressure furnaces involve many constructional problems compared with furnaces operating at atmospheric pressure or lower pressure. The furnace per unit of space must be enclosed in a pressure chamber capable of confining gas under high pressure. This means that the cost of the furnace volume will be high. The cost increases rapidly with an increased pressure and increased pressure chamber diameter. This means that it is necessary to economize the space in the pressure chamber. The heating of the pressure chamber walls must be limited in view of the strength. In addition, the heat losses must be limited in order to achieve and maintain the desired treatment temperature with a reasonable supply of power. The insulation and the heater inside the pressure chamber between the furnace space and the walls of the pressure chamber must be designed with the least radial extension in order to obtain a maximum furnace space. Designing the furnaces so that a furnace space with a large diameter is obtained in a pressure chamber with a small diameter involves many difficult problems. In the U.S. Pat. Nos. 3,598,378, 3,628,779 and 3,790,339 pressure furnaces of various designs are further described. In all these furnaces there is a heater inside the insulation, which heater contains a metal tube with insulators supporting heating elements. In furnaces for very high temperature of the heaters used so far have been found to possess certain drawbacks. Among other things, deformations have occurred which have led so shortcircuits or other faults and which have made it difficult to exchange the heaters.